Time-dependent release mechanisms of drugs have been described in the literature for tablet, pellet and capsule formulation utilising a wide range of physicochemical and physicomechanical strategies. The common feature of all such formulations is that they are activated by contact with fluids following ingestion by the patient and the drug will be released at the predetermined time after administration. Only after the formulations come into contact with gastric fluids does the ‘clock’ start.
Drug release subsequently takes place at a predicted time, although it will be appreciated that since the dosage unit will be travelling through the GI tract during the lag period, drug release will necessarily be at some unknown GI tract site. Using such formulation strategies, it will be possible to design delivery systems capable of releasing drugs according to chronotherapeutic principles and targeting release to the circadian rhythm of disease states (Stevens H N E, Chronopharmaceutical Drug Delivery. J Pharm Pharmac, 50 (s) 5 (1998))
However, many of the formulations in the art rely on complex structures which can add to the cost of the manufacture of the drug and/or can be subject to malfunction leading to incorrect/inappropriate administration of the drug.
Diclofenac is a non-steroidal anti-inflammatory drug (NSAID) which is taken to reduce inflammation and as an analgesic reducing pain in conditions such as arthritis or acute injury. It can also be used to treat menstrual pain and dysmenorrhea.
Many diclofenac formulations to be taken orally comprise an enteric coating, which minimises direct contact between the drug and the gastric mucosa. It is known that diclofenac is poorly soluble in the stomach due to the acid pH, but more soluble in the alkaline pH of the duodenum. In this manner many such formulations are generally designed to delay release until the formulation passes through the stomach.
U.S. Pat. No. 6,312,724 describes a sustained release formulation comprising diclofenac.
It is amongst the objects of the present invention to obviate and/or mitigate at least one of the aforementioned disadvantages.
It is amongst the objects of the present invention to provide a formulation which may be easily and/or cheaply manufactured and which allows for an active agent to be administered immediately and following a period of delay following administration.